From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754394Ab1G0OeU (ORCPT ); Wed, 27 Jul 2011 10:34:20 -0400 Received: from mail-ey0-f171.google.com ([209.85.215.171]:54422 "EHLO mail-ey0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753564Ab1G0OeS (ORCPT ); Wed, 27 Jul 2011 10:34:18 -0400 Message-ID: <4E3021E6.30409@gmail.com> Date: Wed, 27 Jul 2011 16:34:14 +0200 From: Maarten Lankhorst User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:5.0) Gecko/20110707 Thunderbird/5.0 MIME-Version: 1.0 To: Thomas Gleixner CC: Darren Hart , Linux Kernel Mailing List , Steven Rostedt Subject: Re: rt_mutex: restore wait_lock init in __rt_mutex_init References: <1311754711-19577-1-git-send-email-dvhart@linux.intel.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/27/2011 11:37 AM, Thomas Gleixner wrote: > On Wed, 27 Jul 2011, Darren Hart wrote: > >> Without the raw_spin_lock_init(), the wait_lock does not get properly >> initialized with CONFIG_DEBUG_SPINLOCK. This can manifest in a BUG() in the >> futex requeue_pi path when the pi_state->pi_mutex->wait_lock fails the magic >> test in rt_mutex_start_proxy_lock()->raw_spin_lock(&lock->wait_lock). > That's actively wrong. You reinitialize the lock for all other cases > which call this via rt_mutex_init(). There is a reason why I moved the > spin lock initializer out of __rt_mutex_init() into > rt_mutex_init(). The lock name stuff for lockdep ends up to be > "lock->wait_lock" for all rt_mutexes, which is pretty useless when you > have to analyze a lockdep splat. Thanks for finding it nevertheless. > > So the correct fix is: > > Index: linux-2.6/kernel/rtmutex.c > =================================================================== > --- linux-2.6.orig/kernel/rtmutex.c > +++ linux-2.6/kernel/rtmutex.c > @@ -1296,7 +1296,7 @@ EXPORT_SYMBOL_GPL(__rt_mutex_init); > void rt_mutex_init_proxy_locked(struct rt_mutex *lock, > struct task_struct *proxy_owner) > { > - __rt_mutex_init(lock, NULL); > + rt_mutex_init(lock); > debug_rt_mutex_proxy_lock(lock, proxy_owner); > rt_mutex_set_owner(lock, proxy_owner); > rt_mutex_deadlock_account_lock(lock, proxy_owner); > > Seems to work. I no longer get a warning from pulseaudio either. Also darren, at least on fedora 15 glibc supports requeue_pi. support for that is in nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_*.S Cheers, Maarten